1. Statement of the Technical Field
The present invention relates to the provisioning of Web services and more particularly to an autonomic Web services hosting infrastructure.
2. Description of the Related Art
Web services have become a focal point of technical innovation and new business opportunity. In particular, Web services offer a solution to the interoperability problem for heterogeneous computing systems. Consequently, Web services technology promises to provide computing resources to end users distributed about the global computer communications network based upon a pay-per-use model. Still, the rate of adoption for Web services technology remains inhibited by the complexity involved in deploying new Web services. In particular, providers of Web services hold strong concerns in regard to the availability of deployed Web services.
Specifically, from the perspective of the Web services provider, the unexpected unavailability of a deployed Web service can translate in lost business revenues, though the unexpected unavailability can arise from an excess demand for the deployed Web service which exceeds the capacity of the Web services hosting environment. As a result, typical hosting environments are “over-engineered” to ensure redundancy, quality of service and high availability. Consequently, system engineers find themselves trying to master the delicate and often expensive balance between over-capacity and under-utilization.
To balance both the matter of over-capacity and under-utilization in a Web services hosting environment, typically a communication mechanism is disposed between the gateway nodes the provide the Web services, the Web service deployment agency, and the agency tasked with deciding when to provision a Web service, or to offload the provisioning of the Web service to another host. The communication mechanism can provide critical coordination between the nodes and the agencies so that the tasked agency can effectively balance capacity and utilization of Web services.
Aside from high-availability considerations relating to the capacity of the Web services hosting environment, availability issues also can arise from the failure or mal-operation of a deployed Web services. More particularly, distributed systems as a whole often suffer based upon the characteristics of an individual component. For instance, where one Web service experiences a heavy load or fails altogether, the quality of service (QoS) experienced about the entire distributed system can degrade in quality. Therefore, the more distributed a system, the more Important can be for the distributed system to be “autonomic”.
In the famed manifesto, Autonomic Computing: IBM's Perspective on the State of Information Technology, Paul Horn, Senior Vice President of IBM Research, observed, “It's not about keeping pace with Moore's Law, but rather dealing with the consequences of its decades-long reign.” Given this observation, Horn suggested a computing parallel to the autonomic nervous system of the biological sciences. Namely, whereas the autonomic nervous system of a human being monitors, regulates, repairs and responds to changing conditions without any conscious effort on the part of the human being, in an autonomic computing system, the system must self-regulate, self-repair and respond to changing conditions, without requiring any conscious effort on the part of the computing system operator.
Thus, while the autonomic nervous system can relieve the human being from the burden of coping with complexity, so too can an autonomic computing system. Rather, the computing system itself can bear the responsibility of coping with its own complexity. The crux of the IBM manifesto relates to eight principal characteristics of an autonomic computing system:                I. The system must “know itself” and include those system components which also possess a system identify.        II. The system must be able to configure and reconfigure itself under varying and unpredictable conditions.        III. The system must never settle for the status quo and the system must always look for ways to optimize its workings.        IV. The system must be self-healing and capable of recovering from routine and extraordinary events that might cause some of its parts to malfunction.        V. The system must be an expert in self-protection.        VI. The system must know its environment and the context surrounding its activity, and act accordingly.        VII. The system must adhere to open standards.        VIII. The system must anticipate the optimized resources needed while keeping its complexity hidden from the user.        
Conventional business models increasingly rely upon the use of Web services to maintain cross-platform compatibility, value-chain relationships, customer relationships, and partner relationships. With the rapid undertaking and deployment of Web services, however, focus has shifted to the interoperability of various Web services across the value chain. In furtherance of this effort, the Open Grid Services Architecture (OGSA) has been leveraged to address the problem of support and software maintenance among Web services components distributed about the Web services hosting environment.
Notably, the physiology of a grid mechanism through OGSA can provide protocols both in discovery and also in binding of Web services, hereinafter referred to as “grid services”, across distributed systems in a manner which would otherwise not be possible through the exclusive use of registries, directories and discovery protocols. As described both in Ian Foster, Carl Kesselman, and Steven Tuecke, The Anatomy of the Grid, Intl J. Supercomputer Applications (2001), and also in Ian Foster, Carl Kesselman, Jeffrey M. Nick and Steven Tuecke, The Physiology of the Grid, Globus.org (Jun. 22, 2002), a grid mechanism can provide distributed computing infrastructure through which grid services instances can be created, named and discovered by requesting clients.
Grid services extend mere Web services by providing enhanced resource sharing and scheduling support, support for long-lived state commonly required by sophisticated distributed applications, as well as support for inter-enterprise collaborations. Moreover, while Web services alone address discovery and Invocation of persistent services, grid services support transient service instances which can be created and destroyed dynamically. Notable benefits of using grid services can include a reduced cost of ownership of information technology due to the more efficient utilization of computing resources, and an improvement in the ease of integrating various computing components. Thus, the grid mechanism, and in particular, a grid mechanism which conforms to the OGSA, can implement a service-oriented architecture through which a basis for distributed system integration can be provided—even across organizational domains.
While grid services can be configured to provide an enhanced utilization of computing resources, grid services heretofore have not been able to provide a differential utilization of computing resources. Varying levels of computing services can be provided based upon what has been referred to as a “policy based service differentiation model”. In a policy based service differentiation model, the computing devices can offer many levels of service where different requests for different content or services which originate from different requestors receive different levels of treatment depending upon administratively defined policies. In that regard, a service level agreement (SLA) can specify a guaranteed level of responsiveness associated with particular content or services irrespective of any particular requestor. By comparison, quality of service (QoS) terms specify a guaranteed level of responsiveness minimally owed to particular requesters.
The policy based service differentiation model is the logical result of several factors. Firstly, the number and variety of computing applications which generate requests across networks both private and public has increased dramatically in the last decade. Each of these applications, however, has different service requirements. Secondly, technologies and protocols that enable the provision of different services having different security and service levels have become widely available. Yet, access to these different specific services must be regulated because these specific services can consume important computing resources such as network bandwidth, memory and processing cycles. Finally, business objectives or organizational goals can be best served when discriminating between different requests rather than treating all requests for computer processing in a like manner.
The Web SLA (WSLA) is a proposed specification which defines a markup language for representing assertions by a service provider to guarantee a defined level of service. By comparison, WS-Policy is a proposed specification which provides a general purpose framework for describing and communicating policies and business rules associated with a Web service. As cross-enterprise technologies such as the Web service and the grid services mechanism adopt autonomic principals, the need exists to leverage business rules to govern the self-adapting nature of the Web services hosting environment. In particular, it would be preferable for a Web services hosting environment to be able to detect, in advance, the imminent inability of the Web services hosting environment to meet the contractual requirements of an SLA. In response, it would be preferable to the Web services hosting environment to autonomically heal itself and to undertake remedial measures so as to meet the contractual terms of the SLA.